The invention relates generally to a system and method for delivering a stent. More particularly, the invention relates to a stent delivery system (SDS) and method for delivering a self-expanding stent into a body lumen.
In typical percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral arteries and is advanced therein until the distal tip thereof is in the ostium of the desired coronary artery. A guide wire and a dilatation catheter having an inflatable balloon on the distal end thereof are introduced through the guiding catheter with the guide wire slidably disposed within an inner lumen of the dilatation catheter. The guide wire is first advanced out of the distal end of the guiding catheter and is then maneuvered into the patient""s coronary vasculature containing the lesion to be dilated, and is then advanced beyond the lesion. Thereafter, the dilatation catheter is advanced over the guide wire until the dilatation balloon is located across the lesion. Once in position across the lesion, the balloon of the dilatation catheter is filled with radiopaque liquid at relatively high pressures (e.g., greater than about 4 atmospheres) and is inflated to a predetermined size (which may be the same as the inner diameter of the artery at that location) to radially compress the atherosclerotic plaque of the lesion against the inside of the artery to thereby dilate the lumen of the artery. The balloon is then deflated so that the dilatation catheter can be removed and blood flow resumed through the dilated artery.
A common problem that sometimes occurs after an angioplasty procedure is the appearance of restenosis at or near the site of the original stenosis in the blood vessel which requires a secondary angioplasty procedure or a bypass surgery. Another occurrence which reduces the success of an angioplasty procedure is that frequently the stenotic plaque or intima of the blood vessel or both are dissected during the angioplasty procedure by the inflation of the balloon. Upon deflation of the balloon, a section of the dissected lining (commonly called a xe2x80x9cflapxe2x80x9d) will collapse into the bloodstream, thereby closing or significantly reducing the blood flow through the vessel. In these instances, emergency bypass surgery is usually required to avoid a myocardial infarct distal to the blockage. Side branches, tortuous vessels, and the more distal arteries have also presented serious difficulties in the PTCA procedure because of the balloon diameter.
Conceivably, the dilatation catheter could be replaced with a perfusion-type dilatation catheter such as described in U.S. Pat. No. 4,790,315 in order to hold the blood vessel open for extended periods. However, some perfusion-type dilatation catheters have relatively large profiles which can make advancement thereof through the blockage difficult, and therefore immediate bypass surgery may be the only means of avoiding an infarct distal to the blockage. Additionally, the inflated balloon of some perfusion-type catheters can block off a branch artery, thus creating ischemic conditions in the side branch distal to the blockage.
In response, one particular endoprosthetic device, known as a stent, has been developed to prevent restenosis and repair damaged vessel walls. Stents are generally tubular-shaped intravascular devices having an expandable or self-expanding structure that is placed within a damaged artery to hold it open. They are particularly suitable for supporting and holding back a dissected arterial lining which could otherwise occlude the fluid passageway there through. The use of stents in non-invasive interventional cardiology has proven to have many advantages, including a net gain in Minimal Lumen Diameter (MLD) of the vessel and reduced restenosis rates.
Stents typically are constructed in one of two general configurations: expandable and self-expanding. Expandable stents require a mechanical force, such as exerted by a balloon disposed within the stent interior, to increase in diameter. Self-expanding stents are generally constructed of shape-memory materials that are biased so that the stent diameter will increase from a reduced diameter maintained by constraining forces to an expanded diameter once the constraining forces are removed, without the action of any external mechanical forces. Some self-expanding stents maintain a reduced diameter at a first temperature range but increase to an expanded diameter at a second temperature range.
Self-expanding stents may be formed in a variety of configurations, and such stents made of coiled wire or springs, braided wire or mesh, and fence-like structures configured in a zig-zag pattern are known in the art.
Delivery systems for self-expanding stents often include a stent circumferentially surrounding the distal end of a delivery catheter. Due to the narrow passageways within the vascular system and particularly the stenotic regions, stents are generally confined in a reduced radius for delivery to the deployment site. Therefore, it can be desirable to keep the profile of the catheter as small as possible to minimize the radius of the stent mounted thereon. For delivery purposes, these stents are typically held in a minimal diameter state by some structure such as a sheath. Upon displacement of the sheath, the stent is exposed to self-expand and contact the vessel wall. Once the stent is deployed, the catheter is removed, leaving the stent implanted at the desired location to keep the vessel walls from closing and allowing time to heal. Another device secures the stent to a catheter without the use of a sheath.
The optimum catheter length for stent delivery can vary depending on the particular procedure, the patient, and the physician. In order to ensure that physicians have a full selection of catheter lengths from which to choose, hospitals often must keep a large inventory of different catheter lengths in stock. Even with such a large stock, however, a physician may find that the hospital does not have the particular length desired. For example, a physician performing a stent deployment procedure in the left common iliac may decide to deliver the catheter contralaterally over the aortic bifurcation, and may desire a catheter having a length of 50 cm for the particular procedure. If the shortest delivery catheter in the hospital""s inventory has a length of 80 cm, the physician will often have to make do with the available catheter. The excess catheter length can be awkward for the physician to use, particularly when compared to the optimal length desired by the physician.
During stent delivery procedures, physicians may desire to place the catheter handle on a suitable surface, such as a patient""s leg. To meet such needs, some catheter handles have been designed with a platform on one side that is designed to provide stability when the handle is placed on a patient""s leg or other suitable surface. However, during some procedures the physician may instead desire to keep the catheter handle in his or her hand, as may be the case where no suitable surface is available on which to place the catheter handle. However, the stability platform that improves the ability of the catheter handle to rest on a surface may feel awkward to a physician who prefers to maintain the catheter handle in his hand.
What has been needed and heretofore unavailable is a stent delivery system with a catheter length and catheter handle configuration that can be selectively varied by the physician, thereby providing the physician with an optimal catheter length and catheter handle configuration while avoiding the need for a hospital to maintain large inventories of catheters with different lengths and handles. The present invention satisfies these needs as well as others.
The present invention is directed to a device and method for delivering a self-expanding stent using a catheter to deliver and deploy the self-expanding stent, which is particularly suitable for use in coronary arteries to hold vessels open after a balloon angioplasty procedure.
The stent delivery system in accordance with the present invention includes a catheter having an inner member and an outer member. The inner member and outer member are both able to flex in order to traverse tortuous lumens, but the outer member has relatively little or no compliance (that would otherwise permit a self-expanding stent within the outer member to expand radially outwardly.) A stent positioned within the outer member cannot appreciably expand.
In one embodiment of the invention, the self-expanding stent is forced into a constrained position having a low profile or reduced cross section and positioned between the inner member and the outer member of the variable-length catheter.
The stent delivery system includes a mechanism for cutting the catheter to a desired length. The cutting mechanism may cut the outer member, the inner member, or both. In one embodiment of the invention, the cutting mechanism utilizes one or more blades whose cutting edges are configured to engage the outer member along a cutting line running generally parallel to the outer member longitudinal axis. The blade or blades can be advanced longitudinally along the outer member to split apart the outer member.
The stent delivery system further includes a deployment mechanism that serves to hold the inner member secure while the outer member is retracted during stent deployment. The stent delivery system may also include a slider mechanism that permits the cutting mechanism and/or deployment mechanism to be slidably advanced along the catheter.
In one embodiment of the invention, the delivery system includes a combined cutter/slider/deployment mechanism. The cutter/slider/deployment mechanism is slidably secured to a proximal portion of the catheter. The cutter/slider/deployment mechanism is configured so that, as it is slidably advanced along the catheter, excess length of the catheter is cut away from the proximal catheter end. Accordingly, by advancing the cutter/slider/deployment mechanism distally along the catheter, a user can shorten the catheter to a desired length.
In order to allow accurate adjustment of the catheter length, the catheter may include length markings on the catheter itself. A length measurement system may be provided on the catheter packaging.
With the catheter length adjusted to the desired length, the catheter and stent are then introduced into a body lumen and advanced to the treatment site. Once the stent is in the desired position, the outer member can be retracted relative to the stent, so that the stent is no longer restrained by the outer member. The stent can thus expand. The relative movement of the stent and outer member may involve sliding the stent forward along the catheter until it exits the outer member, or withdrawing the outer member along the catheter, or a combination of both. For example, the sliding out of the stent may be accompanied by a simultaneous, equal, and/or and opposite withdrawal of the outer member from the treatment site, so that the stent remains distally motionless with respect to the treatment site. When the stent exits the outer member, the stent can fully deploy into contact with the arterial wall and provide structural support thereto.
In an embodiment where the stent is held fixed relative to the desired treatment location, the outer member slides proximally relative to the desired treatment location, with the stent remaining still with respect to the treatment/deployment location. As the outer member is retracted, the stent expands.
In a further embodiment of the invention, the catheter handle is provided with a removable platform that is configured to improve the stability of the catheter handle when place on a suitable surface, such as on the leg of the patient. The removable platform is releasably secured to the catheter handle, and may be removed in various ways, such as by sliding the removable platform proximally off of the catheter handle.